Photo quality for a book

I plan to publish a book on martial arts (a printed book, but I am also thinking of an ebook). It will contain a lot of photos describing the individual techniques.

My question is: what quality of photos do I need to make for the book to look good? Can I use a conventional digital camera? Or do I need professional equipment, such as studio, lighting, etc.? Should I take the pictures myself or find a professional?

Notice that there will be a lot of pictures in the book; and photographing them will take a lot of time.